The invention relates to couplings for winding and unwinding mandrels and like rotary driven members. More particularly, the invention relates to improvements in couplings of the type wherein the connection between a rotary driving member (such as a motor-driven shaft) and a rotary driven member (such as a mandrel) can be interrupted by pivoting a first section of the end portion of the driving member relative to a second section in order to allow for sidewise extraction of the end portion of the driven member from a recess in the end portion of the driving member.
A coupling of the just outlined character is disclosed, for example, in the aforementioned U.S. Pat. No. 4,344,304 as well as in German Pat. No. 917,592. The German patent discloses a coupling wherein the square end portion of a rotary mandrel is receivable in a complementary recess in the end portion of the driving member. The end portion of the driving member has a pivotable hand wheel which can be moved between an inoperative position, wherein the hand wheel permits insertion of the end portion of the mandrel into the recess, and an operative position in which the driving member is ready to transmit torque to the mandrel. The configuration of the end portion of the driving member is such that the hand wheel is compelled to automatically assume its operative position when the end portion of the mandrel extends into the recess and the motor for the driving member is started so that the driving member begins to transmit torque to the mandrel by way of surfaces surrounding the recess in the end portion of the driving member. Before the hand wheel is pivoted to its operative position, three facets on the end portion of the mandrel are adjacent to three complementary surfaces in the recess of the end portion of the driving member. The surface surrounding the recess is circumferentially complete when the hand wheel is pivoted back to its operative position. In other words, the fourth facet of the end portion of the mandrel is engaged by a complementary facet of the driving member in response to pivoting of the hand wheel to its operative position.
A drawback of the patented coupling is that the mandrel must be absolutely parallel to the driving member during introduction of the end portion of the mandrel into that part of the recess which is defined by the non-pivotable section of the end portion of the driving member. This cannot be readily achieved when the patented coupling is one of two couplings which are provided at opposite axial ends of a driven member in the form of a mandrel having a length of between one and three meters. At such time, it is necessary to employ two workers one of whom monitors the introduction of one end portion of the mandrel into the recess of the first coupling while the other worker monitors the introduction of the other end portion of the mandrel into the recess of the second coupling. If the two couplings are constructed and assembled with a reasonably high degree of precision, such simultaneous introduction of both end portions of the mandrel into the recesses of the respective discrete couplings is practically impossible. Nevertheless, such couplings are in use because they exhibit the advantage that the hand wheels at both axial ends of the mandrel are reliably pivoted to their operative positions in response to starting of the respective driving members.
U.S. Pat. No. 3,147,985 to Hornberger et al. discloses a driving chuck wherein the square end portion of a driven spindle is received in the recess of the end portion of a rotary driving member in response to shifting of a slip ring axially of the end portion of the driving member to a retracted position. Once the end portion of the spindle is properly inserted in that portion of the recess which is defined by the end portion of the driving member, the slip ring is pushed back axially of the driving member to assume an operative position in which it cooperates with the end portion of the driving member to define a recess bounded by a circumferentially complete internal surface which is capable of transmitting torque to the faceted peripheral surface of the end portion of the spindle. The end portion of the driving member defines a first portion of the recess, and such first portion is bounded by two internal surfaces which make an angle of approximately 90 degrees and abut two complementary facets of the end portion of the spindle when the latter is properly inserted into the recess in retracted position of the slip ring. The just described configuration of the recess in the end portion of the driving member is desirable and advantageous because the end portion of the spindle is automatically centered in the first portion of the recess before the slip ring is shifted back to its operative position.
A similar coupling for transmission of torque between a rotary driving member and a rotary driven member is disclosed in German Pat. No. 29 32 895 wherein the end portion of the driven member has a substantially triangular cross-sectional outline. The end portion of the driving member has a recess surrounded by a substantially V-shaped surface which must be oriented in such a way that the apex of the V is located at the lowermost point of the recess when the end portion of the driven member is ready for insertion into the recess. Such construction ensures that the end portion of the driven member can be properly received in the recess of the end portion of the driving member, even if the surfaces bounding the end portion of the driven member and the recess are not machined with a high degree of precision. Thus, the end portion of the driven member automatically finds its way into the recess even if the recess is bounded by surfaces which are not exactly complementary to the corresponding surfaces of the end portion of the driven member. Therefore, the end portion of the driven member can be inserted into the recess or extracted from the recess by an automatic mechanism. This is particularly desirable when the driven member is a mandrel which is to carry one or more reels for collection or for paying out of elongated webs, strips or ropes of filamentary or other material. As mentioned before, the manipulation of certain presently known elongated mandrels for winding up or paying out of such elongated web or rope-shaped materials necessitates the presence of two workers.
The couplings which are disclosed by Hornberger et al. and in the just discussed German Pat. No. 29 32 895 exhibit the drawback that the transmission of torque from the driving member to the driven member is possible only when the pivotable, reciprocable or otherwise movable section of the end portion of the driving member is moved to operative position. With reference to the coupling of Hornberger et al., this means that the driving member can transmit torque to the driven member only when the two-piece slip ring is returned from its retracted to its operative position so that the slip ring defines a portion of the surface surrounding the peripheral surface of the end portion of the driven member. If the slip ring is not returned to its operative position when the driving member is set in rotary motion, the end portion of the driven member is likely to be expelled from that portion of the recess which is defined by the end portion of the driving member. The thus displaced or shifted end portion of the driven member prevents the movement of the slip ring back to its operative position and is likely to cause a lengthy interruption of operation of the winding or unwinding apparatus. Moreover, if the driving member is set in rotary motion before the slip ring returns to its operative position, the improperly inserted end portion of the driven member can cause extensive damage to the coupling as well as to other component parts of the apparatus in which the patented coupling is put to use.
An attempt to overcome the drawbacks of the couplings of Hornberger et al. and German Pat. No. 29 32 895 is disclosed in German Pat. No. 31 27 553. The patented coupling is provided with a mechanism which moves the pivotable hand wheel to its operative position before the driven member can receive torque from the driving member. The arrangement is such that the end portion of the driven member cannot be expelled from or shifted relative to the recess in the non-movable end portion of the driving member before the hand wheel reassumes its operative position. A drawback of this patented proposal is that the means for monitoring the position of the hand wheel and for moving the hand wheel to its operative position in automatic response to starting of the driving member is expensive and occupies an excessive amount of space.
The danger of failure of a conventional coupling is particularly pronounced if the end portion of the driven member is surrounded, either in part or entirely, by circular or convex surfaces. The totality of such surfaces can form a substantially conical surface which has an outline resembling the outline of the internal surface in the recess in the end portion of the driving member. At such time, the transmission of torque takes place by way of a single flat or by way of two or more relatively small facets forming part of the peripheral surface of the end portion of the driven member and the internal surface bounding the recess in the end portion of the driving member.